Hot fuel pump fuse

[Stephen B]

I have not found a definitive answer for this on multiple searches so I figured I'd ask the pros:

The 16 amp fuel pump fuse on my 930 gets extremely hot and fries about once a month. Last time it burnt the lower fuse tab almost black and cooked about 1" of the output wire. I bypassed the tabs by attaching an external blade style fuse holder to the upper and lower screws. Runs fine again but it's still getting pretty hot. What's causing this?

Additional info: Both fuel pumps are new, connections are corrosion free and protected and the red relays are new. All the chassis ground connections are clean and the alternator output is within spec. Can anyone tell me where the power splits to feed the front and rear pumps? I can't think of anything else to check. My next approach would be to run new wires from each pump all the way to the fuse panel, with a separate fuse for each pump.

Any help would be greatly appreciated!

[jason2guy]

had the same thing happen. ive heard its the actual fuse block location that causes the problem. something about the properties of the metal after all those years of current flowing thru it. what i did was find an empty fuse block location, and move the fuel pump connections to it.

[Stephen B]

Thanks Jason. I don't think I have any spare fuse locations but Pelican does sell replacement blocks. I'll give that a try.

[OSI930]

There is an article in the Tech Articles section by Lee Rice that details how to fix this. The article is titled "Electrical System Upgrades". Just click on the "Tech Info Center" tab at the top of this page and scroll down to the "Gauges, Headlamps, and Electrical" section contained in the "911 Technical Articles". That should get you started.

[Stephen B]

Thanks OSI. Looks like a good approach.

[RoninLB]

Dirty connections cause resistance. This unwanted resistance may cause voltage drop available to the pumps. A quick check is measuring voltage at the battery and different places on the circuit. Anything over 3% I would consider a serious problem in any circuit.

If the battery is 13.9..
On a calcualactor plug in 13.9 x 3% = .417
13.9 - .417 = 13.48

that said the heat is probably from resistance at the wire and fuse box connection, or the fuse connection.

[Stephen B]

Ronin:

I tinned all the wire ends when I added the in line fuse holder. It still gets warm but not hot. I plan on doing the Lee Rice upgrade as soon as I receive the needed parts.

Thanks for all the help gentlemen - it's greatly appreciated!